I have searched on my own and am finding repetitive information that appears to read like a sales pitch on ie., Hydroton and other similar products. Specifically I have seen claims it is "100% clay" and baked expanded clay, which appears to be a misnomer.
There are in nature expansive clays, most are 2:1 type clays. Clays that are expansive, only expand when wet and contract when dry. I am not familiar with the baked "clay" ball grow bed media but assume they are not both compacted into a ball, vitrified in a kiln, and somehow resulting in a porous media. Bricks are made from clay that has been heated. Bricks aren't necessarily known for being porous. I am wondering what benefit there is, if any in using baked clay balls over gravel or other media. Basically as I understand it, the media supports the plants, gives a surface for sludge to adhere to, and drains to allow oxygen exchange. In soils, clay has beneficial properties such as Cation Exchange Capacity (CEC) allowing mineral components essential to plants to be held to the soil particles to later be absorbed by the plants. I am wondering if there is a possibility of these clay balls having CEC, although having been vitrified it is not likely.
Does anyone have any specific info on the make up of the clay balls type media? And is there any significant benefit to using it over gravel or other media?